Which devices connect OSPF areas to the backbone?

• A. Core Routers
• B. Area Border Routers
• C. Stub Routers
• D. Edge Routers

Answer: (C)

In OSPF, the backbone (Area 0) must serve as the central conduit for routing between areas, and the devices that link other areas to that backbone are Area Border Routers. An ABR has interfaces in Area 0 and in one or more non-backbone areas, keeps separate topology databases for each area, and uses type-3 summary LSAs to advertise networks from one area into others. This lets routers in different areas learn about each other’s networks without needing full detail from every area. Terms like core routers or edge routers aren’t formal OSPF roles, and stub routers aren’t the device type that connects areas to the backbone. So the device that connects OSPF areas to the backbone is the Area Border Router.